M2M (machine to machine) is widely applied in multiple fields, such as intelligent traffic, a building automation system, and a video surveillance system. An M2M device basically adopts a battery powered system, and one surveillance network has tens of thousands of M2M devices; therefore, a work load of changing batteries for these M2M devices is quite heavy, so that people expect that an M2M device has low power consumption and long standby time, thereby reducing the number of times of battery change.
For a UE (user equipment) serving as an M2M device, power consumed in an idle state is far less than power consumed in a connected state, and most power consumption in the idle state originates from switching of the UE from the idle state to the connected state.
In the prior art, in order to reduce power consumption of a UE and increase standby time of the UE, a UE in an idle state usually receives a paging message from a network in a DRX (discontinuous reception) manner, so as to reduce the number of switches of the UE from the idle state to a connected state, thereby achieving an objective of saving power. Meanwhile, when an MME (mobility management entity) learns that an SGW (serving gateway) buffers downlink data that needs to be sent to the UE, the MME delays delivering the paging message to the UE or further increases a DRX period of the UE, so as to further reduce the number of switches of the UE from the idle state to the connected state, to enable the UE to remain in the idle state as far as possible, thereby further reducing power consumption of the UE and achieving an objective of saving power.
However, when the MME delays delivering the paging message or the UE uses a long DRX period, because the UE needs to wait for a long time each time before the UE receives the paging message from the MME, establishes a connection to the network according to the paging message, and receives corresponding downlink data, it is possible that an SGW/a PGW (Packet Data Network Gateway) cannot receive connection establishment information of the UE within a normal time interval, and cannot deliver downlink data of the UE to the UE, so that the SGW may mistakenly consider that an error or exception occurs in the network, and further discard the buffered downlink data of the UE.